The design of an antenna for a particular communication system typically involves a consideration of the sought after performance of the system and the tooling costs in manufacturing the reflector elements of which the antenna will be configured. In items of performance, shaped offset (or clear aperture) geometry reflectors enjoy little or no blockage, high illumination efficiency with low spillover, and good control of sidelobes. However, different (unique) tooling is required for each panel, making the overall manufacturing process extremely costly.
The use of centerfed shaped reflectors and unshaped offset reflector, on the other hand, can reduce tooling requirements by a factor of four or five. However, the savings in cost of manufacture suffers a penalty in antenna performance, as efficiency will drop due to either high blockage or greater spillover.